NATS101
Internet Engineering
Fall 2022@1995parham
History
- NATS is a high-performance messaging system created by Derek Collison in 2010
- It was originally built to serve as the message bus for Cloud Foundry
- Handling internal communication among components of the system
It Addresses
- Service Discovery
- Low latency communication
- Load balancing
- Notification and events handling
Overview
- Client publishes message on
foo
subject - Only clients subscribed to
foo
receive the message
How Simple!
INFO {"server_id":"NCNS32OEKOMMHTBVUYC7QWASFAP3BPEKGZG3QDIYRCBUL23WE3OVVBBO","server_name":"NCNS32OEKOMMHTBVUYC7QWASFAP3BPEKGZG3QDIYRCBUL23WE3OVVBBO","version":"2.1.7","proto":1,"git_commit":"bf0930e","go":"go1.13.10","host":"0.0.0.0","port":4222,"max_payload":1048576,"client_id":1,"client_ip":"172.17.0.1"}
SUB greetings 1
+OK
PUB greetings 12
Hello World!
+OK
MSG greetings 1 12
Hello World!
Request/Response
- Client connected to NATS publishes a request on a
help
subject - Worker client subscribed to
help
, processes requests, then sends response - Audit client is subscribed to all subjects via a wildcard, so also receives message but does not reply
- Publisher receieves the response from the worker client
Queue
- Publisher sends multiple help requests on a
help
subject - Multiple worker clients subscribed to the
help
subject from a distributed queue - Each published request is randomly balanced to only one of the worker clients in the distributed queue
NATS As an Always Available Dial Tone
- The main design constraints that define the style of the NATS project are:
- Simplicity
- Performance
- Reliability
- It does not offer any Persistence or Buffering
- It is true Fire and Forget
Availability
- NATS will try to protect itself at all costs to be available for all users
- NATS client libraries, internally try to have an always established connection to one of the available NATS servers
- In case a server fails, NATS will reconnect to another available server in the pool
- NATS supports high-availablity via a clustering mode that is set up as a full-mesh of the servers
Slow Consumer
- By default, if a client fails to drain the pending data that the server is holding for the client for over two seconds, the server will disconnect the client
- Read more about it here
Ping/Pong
- There is a PING/PONG interval happing that the client has to follow otherwise the server will reset the connection in case there are many PONG replies missing.
- Server sends PING messages to client in each interval and client has to respond
- Client also can send PING messages to the server
Subject Names
- The dot character (.) has special meaning as part of the subject
- When using it as part of the subject, we can create namespaces that can be later matched via wildcards
| Subject | Matches |
|---|---|
| foo.*.bar | foo.hello.bar ✅, foo.hi.bar ✅ |
| foo.* | foo.hello ✅, foo.hi.bar ❌ |
| foo.> | foo.hello.bar ✅, foo.hi.bar ✅, foo.hello ✅ |
*: partial or token match wildcard>: full wildcard
Queue Subscribtions: Hands-on
Worker 1 👷
INFO {"server_id":"NARXYLU3XEZSFYCFRV5WJ63GQS5WDV3WC4WAKCYDYY2IBGIETWJADZVS","server_name":"NARXYLU3XEZSFYCFRV5WJ63GQS5WDV3WC4WAKCYDYY2IBGIETWJADZVS","version":"2.1.8","proto":1,"git_commit":"c0b574f","go":"go1.14.8","host":"0.0.0.0","port":4222,"max_payload":1048576,"client_id":4,"client_ip":"172.22.0.1"}
SUB requests workers 5
+OK
MSG requests 5 6
second
Worker 2 👷
INFO {"server_id":"NARXYLU3XEZSFYCFRV5WJ63GQS5WDV3WC4WAKCYDYY2IBGIETWJADZVS","server_name":"NARXYLU3XEZSFYCFRV5WJ63GQS5WDV3WC4WAKCYDYY2IBGIETWJADZVS","version":"2.1.8","proto":1,"git_commit":"c0b574f","go":"go1.14.8","host":"0.0.0.0","port":4222,"max_payload":1048576,"client_id":5,"client_ip":"172.22.0.1"}
SUB requests workers 55
+OK
MSG requests 55 5
first
Publisher ✍️
INFO {"server_id":"NARXYLU3XEZSFYCFRV5WJ63GQS5WDV3WC4WAKCYDYY2IBGIETWJADZVS","server_name":"NARXYLU3XEZSFYCFRV5WJ63GQS5WDV3WC4WAKCYDYY2IBGIETWJADZVS","version":"2.1.8","proto":1,"git_commit":"c0b574f","go":"go1.14.8","host":"0.0.0.0","port":4222,"max_payload":1048576,"client_id":6,"client_ip":"172.22.0.1"}
PUB requests 5
first
+OK
PUB requests 6
second
+OK
Even More Features!
- Jetstream 🚀
- Clustering ✨
- Super-Cluster with Gateways 🗺️
References 📚
- Practical NATS: From Beginner to Pro, Book by Waldemar Quevedo
- NATS Documentation
